(1) Field of the Invention
The invention relates to a tank for the storage of fluids and chemicals subsea.
(2) Description of Related Art
Tanks that are placed subsea must have certain features to ensure their survivability in the environment. They must contain the working fluids, be compensated to the outside environment and related hydrostatic pressure, and remain intact and in service for the length of their intended mission.
U.S. Pat. No. 7,424,917, which is incorporated herein by this reference, discloses a subsea pressure compensation system which includes a chamber with a piston therein acted on an exposed side by sea water, to provide operational hydraulic fluid for operating a subsea device, with a piston rod having an end in a separate chamber acted on by a fluid to compensate for a pressure differential between the pressure of the water on one piston side and the pressure of the operational hydraulic fluid on the other piston side. However, this reference does not teach, nor suggest, using any of the compensator system or system of pumps to act upon the compensator itself as a self-contained method to test or measure the integrity of the compensator itself, or of any of the barriers that separate the internal fluid from the surrounding outside fluid.
U.S. patent application No. 20080210434A1, which is incorporated herein by this reference, discloses a subsea and modular tanker-based hydrocarbon production system comprising a plurality of interlinked individual tank units which is wholly submersible. However, this reference does not teach, nor suggest, utilizing a pump to generate either a fluid pressure or vacuum to measure the integrity of the walls of the tank.
U.S. patent application No. 20130167962A1, which is incorporated herein by this reference, describes a pressure compensator for a subsea device that embodies the ability of the subsea tank to remain pressure compensated. However, this reference does not teach, nor suggest, using the fluid that is contained between the walls of the compensator to be used in a test protocol to assure the integrity of the wall, or barrier, of the compensator or vessel.
U.S. patent application No. 20150246770A1, which is incorporated herein by this reference, discloses a subsea storage tank, including a body having a storage space therein and formed of light weight concrete inner and outer sides of which are watertight coated or plated. However, this reference does not teach or suggest provisions that allow for the pressurization or vacuum of fluid between the tank inner and outer sides, nor could the fluid in this location be used to test the integrity of either wall of the storage tank or the integrity of the seals of the separation unit.
In light of the foregoing, a need remains for a modular subsea tanker hydrocarbon system, having a dual wall tank, and a barrier bladder, and utilizing a pump to generate either a fluid pressure or vacuum to measure the integrity of both the walls of the tank, and the barrier bladder, to sea water or working fluid.